Create raft_core_corr.py

raft_core_corr.py

@@ -0,0 +1,91 @@
+import torch
+import torch.nn.functional as F
+from raft_core_utils_utils import bilinear_sampler, coords_grid
+
+try:
+    import alt_cuda_corr
+except:
+    # alt_cuda_corr is not compiled
+    pass
+
+
+class CorrBlock:
+    def __init__(self, fmap1, fmap2, num_levels=4, radius=4):
+        self.num_levels = num_levels
+        self.radius = radius
+        self.corr_pyramid = []
+
+        # all pairs correlation
+        corr = CorrBlock.corr(fmap1, fmap2)
+
+        batch, h1, w1, dim, h2, w2 = corr.shape
+        corr = corr.reshape(batch*h1*w1, dim, h2, w2)
+        
+        self.corr_pyramid.append(corr)
+        for i in range(self.num_levels-1):
+            corr = F.avg_pool2d(corr, 2, stride=2)
+            self.corr_pyramid.append(corr)
+
+    def __call__(self, coords):
+        r = self.radius
+        coords = coords.permute(0, 2, 3, 1)
+        batch, h1, w1, _ = coords.shape
+
+        out_pyramid = []
+        for i in range(self.num_levels):
+            corr = self.corr_pyramid[i]
+            dx = torch.linspace(-r, r, 2*r+1, device=coords.device)
+            dy = torch.linspace(-r, r, 2*r+1, device=coords.device)
+            delta = torch.stack(torch.meshgrid(dy, dx), axis=-1)
+
+            centroid_lvl = coords.reshape(batch*h1*w1, 1, 1, 2) / 2**i
+            delta_lvl = delta.view(1, 2*r+1, 2*r+1, 2)
+            coords_lvl = centroid_lvl + delta_lvl
+
+            corr = bilinear_sampler(corr, coords_lvl)
+            corr = corr.view(batch, h1, w1, -1)
+            out_pyramid.append(corr)
+
+        out = torch.cat(out_pyramid, dim=-1)
+        return out.permute(0, 3, 1, 2).contiguous().float()
+
+    @staticmethod
+    def corr(fmap1, fmap2):
+        batch, dim, ht, wd = fmap1.shape
+        fmap1 = fmap1.view(batch, dim, ht*wd)
+        fmap2 = fmap2.view(batch, dim, ht*wd) 
+        
+        corr = torch.matmul(fmap1.transpose(1,2), fmap2)
+        corr = corr.view(batch, ht, wd, 1, ht, wd)
+        return corr  / torch.sqrt(torch.tensor(dim).float())
+
+
+class AlternateCorrBlock:
+    def __init__(self, fmap1, fmap2, num_levels=4, radius=4):
+        self.num_levels = num_levels
+        self.radius = radius
+
+        self.pyramid = [(fmap1, fmap2)]
+        for i in range(self.num_levels):
+            fmap1 = F.avg_pool2d(fmap1, 2, stride=2)
+            fmap2 = F.avg_pool2d(fmap2, 2, stride=2)
+            self.pyramid.append((fmap1, fmap2))
+
+    def __call__(self, coords):
+        coords = coords.permute(0, 2, 3, 1)
+        B, H, W, _ = coords.shape
+        dim = self.pyramid[0][0].shape[1]
+
+        corr_list = []
+        for i in range(self.num_levels):
+            r = self.radius
+            fmap1_i = self.pyramid[0][0].permute(0, 2, 3, 1).contiguous()
+            fmap2_i = self.pyramid[i][1].permute(0, 2, 3, 1).contiguous()
+
+            coords_i = (coords / 2**i).reshape(B, 1, H, W, 2).contiguous()
+            corr, = alt_cuda_corr.forward(fmap1_i, fmap2_i, coords_i, r)
+            corr_list.append(corr.squeeze(1))
+
+        corr = torch.stack(corr_list, dim=1)
+        corr = corr.reshape(B, -1, H, W)
+        return corr / torch.sqrt(torch.tensor(dim).float())